DTC C1237 High System Supply Voltage. Chevrolet PJJ 2000

For 1990-2009 cars

### Circuit Description

The EBCM monitors the switched battery voltage level available for ABS/ETS operation. If the voltage level is too high, damage may result in the system. When the EBCM detects a high voltage condition, the EBCM turns OFF the system relay which removes battery positive voltage from the solenoid valves and the pump motor.

### Conditions for Running the DTC

The vehicle speed is greater than 8 km/h (5 mph).

### Conditions for Setting the DTC

The switched battery voltage is greater than 17 volts for 0.72 seconds.

### Action Taken When the DTC Sets

The following actions occur:

• | The EBCM disables the ABS for the duration of the ignition cycle.

• | The ABS warning indicator turns ON.

• | A malfunction DTC is stored.

### Conditions for Clearing the DTC

• | The condition for setting the DTC is no longer present and the scan tool Clear DTCs function is used.

• | The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

### Diagnostic Aids

The following are possible causes of the DTC:

• | A charging system malfunction.

• | An internal EBCM malfunction.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step uses the scan tool to check the battery positive voltage circuit to the EBCM.

2. This step checks the battery positive voltage supply circuit.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | Go to ABS Diagnostic System Check

2

1. Turn OFF all of the accessories.
2. Install a scan tool.
3. Start the engine.
4. Run the engine at approximately 2000 RPM.
5. With a scan tool, observe the Switched Battery Voltage parameter in the ABS data list.

Does the scan tool indicate that the switched battery voltage is less than the specified voltage?

17 V

Go to Step 5

Go to Step 3

3

1. Turn OFF the ignition.
2. Disconnect the EBCM harness connector.
3. Install the J 39700 universal pinout box using the J39700-99 cable adapter to the EBCM harness connector only.
4. Start the engine.
5. Run the engine at approximately 2000 RPM.
6. Measure the voltage at the J 39700 universal pinout box between the battery positive voltage circuit of the EBCM and a good ground.

Does the voltage measure less than the specified value?

17 V

Go to Step 4

Go to Charging System Diagnostic System Check in Engine Electrical

4

1. Use the scan tool in order to clear the DTCs.
2. Carefully test drive the vehicle at a speed above 8 km/h (5 mph).

Does the DTC reset?

--

Go to Step 5

System OK

5 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement. Did you complete the repair? | -- | Go to Step 6 | --

6

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the conditions for Running the DTC as specified in the supporting test.

Does the DTC reset?

--

Go to Step 2

System OK